Overall, it was a tough week in the European zone for credit investors, although it ended on a somewhat brighter note.  The Markit iTraxx Western Europe Sovereign index, which monitors credit-default swap spreads for the region, started the week at a record 171.5 basis points, then scaled new highs, before finally ending down at 168 bps.The rise in the index reflects growing sovereign debt worries in the euro zone, as investors remained concerned that Ireland will need to tap some form of aid in 2011. Then there is Greece, which is facing its own challenge in getting a budget passed, Italy's government also looks fragile, and Spain is facing stalling economic growth.The result was a rise in yield spread between German bunds and peripheral bonds, with Irish spreads reaching a record 630 bps, before ending the week at 540 bps.EU finance ministers clarified on Friday that any likely burden-sharing by bond-holders, a move pushed by Germany, will not happen before 2013. And there were talks that a bail-out for Ireland was imminent. Both these soothed sentiment on Friday.Data from CMA showed some of the Irish banks and institutions were among the biggest beneficiaries of the improvement in sentiment. The troubled Allied Irish Bank saw a 21 per cent improvement in five-year spreads, to 2597 bps, down 693 bps.With the G20 summit behind us now, the coming week should see more action from the euro zone. Greece's deficit numbers are due to be revised this week, even as the EU, IMF and ECB convene in Athens to assess progress made in meeting the 2010 deficit target. Then there are revisions likely to the "haircut" requirements on Portuguese debt. All this is happening as the market waits to get some confirmation on a possible Irish bailout.Taking a parochial view, claims by Australian banks on banks in Ireland are US$6 billion, Bank for International Settlements data shows.